The Zaguan is one of the major elements of a bahay na bato. It is the space where the family’s carriages are stored. This area is usually finished with Piedra china or Chinese stone. In modern times, this would be the carport.
During the Spanish Colonial Period of the Philippines, families often go to churches and participate in processional carriages. That is why carriages are an important part of the family’s life and so is the space where it is kept. Thus, the zaguan.
In other areas of the world with Spanish influence like Mexico, the zaguan is a central passageway leading to a courtyard. In the Philippines, however, it is a carport that is underneath the living space of the house.
Notice how the Philippine bahay na bato has a strict demarcation of spaces. There is a space for the living area which is found on the upper level and a space for the storage area found at the lower level where the zaguan and other storage spaces are found. One could say this was a Filipino architectural evolution. With a living area above, and a storage below, doesn’t it remind you of the bahay kubo?
References:
“A Study on the Spatial Composition influenced by climatic conditions in 19C Bahay na Bato around Cebu city in Philippines”. <https://www.koreascience.or.kr/article/JAKO201304260598447.page>